This present invention relates generally to signal transmission cable structures for electronic devices and particularly to improving the performance and construction of such a cable structure for high speed data transmission.
The use of electronic devices of all kinds is ever increasing, which has led to a significant increase in the demand for improved components utilized with such devices. One facet in the utilization of such electronic devices involves networking multiple devices together and establishing data communications between the various devices within a networked system. For example, many electronic devices may be coupled together and synchronized with other electronic devices, such as a central control system or computer. Data is transmitted at very high speeds between the networked devices within a system.
For fast and accurate data and information transmission in a networked system, the individual system devices must be optimized when they are networked together so that the system functions at a suitable performance level. Particularly, the interface components of the devices in the system, which allow the various electronic devices to be networked, must be optimized for greater speed and performance. One particularly important interface or interconnect component is the transmission cable which extends between the electronic devices that are communicating. Various cable designs have been utilized for such data and information transmission.
Generally, suitable cable structures utilize a plurality of electrical conductors and a connector structure at one or both ends which interfaces with a networked electronic device. For example, connectors of a cable might plug into appropriate socket structures in the electronic devices. In many applications, the cables are arranged in a high density cable arrangement which is configured to plug into a central backplane which includes a large number of sockets. Data cables include signal conductors, that is, transmission lines which carry the actual data or information signals, and ground conductors which provide an electrical reference for the transmitted data and information.
While the construction of existing cable structures has been suitable for maintaining the integrity of the data signals transmitted thereon, significant attention has still been paid to the termination components or connectors of the cable structure. The connectors of the cable structure provide an electrical transition between the individual electrical conductors of the cable structure, and hence the transmitted signals, and the internal circuitry of the electronic device to which the cable structure is connected. Generally, such connectors utilize a plurality of conductive contacts, often in the form of metal strips, pins and/or tabs. The signal and ground conductors of the cable terminate at the contacts of the connector, and are electrically coupled to the contacts. The electronic device or backplane, into which the connector is plugged, then includes its own set of contacts, such as pins or tabs within a socket, for example, for interfacing with the contacts of the cable connector. Typically, the connector will engage the socket in the traditional male-female relationship. However, various other different connector structures have been utilized as evidenced by numerous patents in the field directed to connector designs.
In existing high speed data cable structures, the contacts of the connector are often housed in an individual plastic, insulative housing piece. The individual cables are then attached to the contacts in the housing piece, such as by soldering the cable conductors to the contacts. Thereafter, the rest of the plastic connector housing, such as in the form of a flat wafer, is molded over the housing piece, over the contacts and over sections of the cables to form the complete connector housing. The connector housing interface with the cables couples the housing to the cables to provide strain relief to the contact/conductor connection. This helps to prevent the cables from being pulled from the connector. A metal shield might also be placed over a side of the connector body is some designs to eliminate electrical interference and crosstalk from affecting the cable at the site of the connector. In currently available designs, the connector housing is thin, such as a 2 millimeter thick wafer, so that high densities of connectors may be stacked next to each other and plugged into a socket.
The manufacturing of the connector, and particularly the molding of the wafer housing over the ends of the cables and over the individual housing piece and contacts, exposes the cable ends to significant heat and pressure associated with the molding process. This degrades the overall integrity of the cable structure. First, the pressure of the mold tends to pinch and smash the ends of the cables where they engage the connector housing and contacts. The cables, which may have a circular cross section, are smashed into oblong cross sections at their ends. This affects the integrity of the insulation of the cable and the conductors, such as the metal braid which surrounds the center conductor in a coaxial cable. Furthermore, the heat of the process only enhances the physical deformation of the cables. Such mechanical damage to the cables affects the electrical integrity of the overall cable structure. For example, cable disconnections at the connector and/or short circuits may result due to the mechanical damage from the molding process. As a result, the cable structures are less robust. Furthermore, the integrity of the data signal sent over the cable may be affected. Cable structures used for high speed data transmission (e.g. rates as high as 1 Gigabit/second) are particularly susceptible to mechanical damage, because the high frequency signals are more sensitive to variations in the mechanical and electrical features of the cables which may exist at the connector termination.
It is therefore desirable to make cable structures for high speed data transmission which are mechanically and electrically more sound than existing cable structures. To that end, attempts have been made to reduce the affects of the manufacturing process on the electrical integrity of the cable structure. Furthermore, efforts are always ongoing to improve the electrical characteristics of the cable and to improve the quality of the signal and ground connections. Attenuation reduction and crosstalk reduction are particular goals for high speed data cables. Also tight signal skews and better reliability are also desirable characteristics.
Therefore, it is desirable to have a cable structure for high speed data communication which has improved signal integrity through the connector of the cable structure.
It is also desirable to have a mechanically and electrically robust and reliable cable structure and connector.
Furthermore, it is desirable to reduce the mechanical and electrical damage to a cable structure incurred during manufacturing and installation of the connector on the cable structure.
It is further desirable to have a connector design which is sufficiently compact, but which maintains a useful density of signal conductors for high speed data applications.
These objectives and other objectives will become more readily apparent from the summary of invention and detailed description of embodiments of the invention set forth herein below.
A cable structure in accordance with the principles of the present invention comprises one or more cables terminating in a connector. The connector comprises a housing with a front end and a rear end and including a plurality of electrical contacts positioned within the housing proximate the front end. The contacts of the connector are configured for engaging the corresponding contacts of an electrical device when the cable structure is coupled to the device. The conductors of the cable, such as a signal conductor and a ground conductor, terminate in the connector housing. Specifically, the conductors are each electrically coupled to a respective housing contact. A signal conductor of the cable connects to a signal contact, and the ground conductor connects to a ground contact, in one embodiment of the invention.
The cable structure may further comprise a metal shield positioned on one face of the housing. The shield is electrically coupled to the ground contact for electrically grounding the shield through the ground contact. Alternatively, the ground conductor of the cable may be connected directed to the shield, wherein the shield is then connected to the contact to thereby define the ground contact.
The connector housing that supports and houses the contacts is coupled with sections of the various cables rearwardly of the contacts. In one embodiment, a portion of the connector housing is molded around the sections of the cables to thereby couple the housing to the sections of the cables. In accordance with one aspect of the present invention, a protective clamp is interposed between the connector housing and the cable sections which are coupled to the connector housing. The protective clamp, which may be formed of a rigid material such as metal, provides mechanical protection for the cable sections to reduce damage thereto which may result from molding or otherwise forming the connector housing over sections of the cables. Specifically, the protective clamp protects the cable sections over which a portion of the housing is molded, to thereby reduce the effects of the heat and pressure of the molding process on the individual cables of the cable structure. The cable structure may include one or more cables, and therefore, the protective clamp may be appropriately sized for use with one or multiple cables.
In one embodiment, the protective clamp comprises two parts or portions which are similarly formed to create a clamshell structure which fits over the cable sections. The parts are appropriately configured to overlay the various cables. Tabs on either end of the individual clamp parts are adjacent to each other when the clamp is in position. Apertures are formed in the tabs so that when the connector housing is molded around the protective clamp and coupled with the cable sections under the clamp, molten plastic flows through the apertures, thereby locking the clamp together and coupling the clamp with the connector housing and the cables.
In another aspect of the present invention, an open window section is formed in the housing and is positioned between the contacts and the protective clamp. The open window section exposes other sections of the cables to further reduce damage to the cable when the connector housing is molded therearound. That is, the open window section eliminates a portion of the connector housing which would otherwise engage the cable sections and thereby eliminates exposure of those cable sections to the heat and pressure of the molding process. The open window section, and the protective clamp, in combination, have been found to improve the overall integrity and robustness of the cable structure. Alternatively, the protective clamp may be utilized alone without an open window section. To that end, the clamp may be dimensioned in length to cover the sections of the cables which would otherwise be susceptible to damage from the heat and pressure of the housing molding process.
One suitable connector housing for the cable structure of the invention is a thin, wafer-like shape with a thickness of approximately 2 milimeters. With such a connector housing, multiple connectors may be stacked together in high density fashion to interface with a device, such as a socket. The cable structure further comprises one or more latch tabs which are coupled to the connector housing. The latch tabs are configured for being engaged by a latch structure when a cable structure is coupled to an electrical device, such as a socket, for securing the cable structure in the socket in a high density cable arrangement. These and other features of the invention will become more readily apparent from the Detailed Description below.